Unbuckling the Van Allen Belts: from Discovery to Modern Models ESAC

ESAC – Science Seminar

Unbuckling the Van Allen Belts: from Discovery to Modern Models

Lionel Métrailler Swiss National Trainee at ESAC (Madrid) INTEGRAL Science Operation Centre (ISOC)

25th of July 2019

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 1/34 ➔ ESAC – SCIENCE SEMINAR Earth’s Magnetic Field Discovery

• Magnetic compass, China, year <1000

• Magnetic declination discovery, China, ~1000

• Earth is a magnet, 1st “terrella”, William Gilbert, 1600

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 2/34 ➔ ESAC – SCIENCE SEMINAR Earth’s Magnetic Field Disturbances

• Disturbances in compass measurements, George Graham, 1724

• Link with Sun spots, Edward Sabine, 1852

• Magnetic storms and solar events link confirmed, Carrington, Sep 1, 1859

• +17h: magnetic storm & low latitude auroras (Tahiti)

• Sun à Earth charged particles transfer

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 3/34 ➔ ESAC – SCIENCE SEMINAR

Frederic Edwin Church

Aurora Borealis

1865

Oil on Canvas

142.3 cm x 212.2 cm

Smithsonian American Art Museum, Washington DC

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 4/34 ➔ ESAC – SCIENCE SEMINAR Charged Particles Motion

• Confirmation of Aurora, ”terrella” experiment, Kristian Birkeland, 1896

Tromso Museum, Norway

Birkeland experiment

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 5/34 ➔ ESAC – SCIENCE SEMINAR Charged Particles Motion

Carl Stoermer, 1903-1955

• Mathematical model

• No analytical solution

• Stable trajectories

• Theoretical links

• Solar charged particles

• Trapped particles

• Magnetic storms

• Ring currents

• Aurora

Stoermer & Birkeland, 1910

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 6/34 ➔ ESAC – SCIENCE SEMINAR First Measurements

Explorer 1, February 1st 1958, first US satellite:

• 360 – 2500 km altitude orbit

• Hint of the inner proton belt.

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 7/34 ➔ ESAC – SCIENCE SEMINAR First Measurements

Explorer 1, February 1st 1958, first US satellite:

• 360 – 2500 km altitude orbit

• Hint of the inner proton belt.

The three men responsible for the success of Explorer 1. From left, William H. st Pickering, James Van Allen, and Wernher von Braun. © NASA. February 1 , 1958 at 03:48 UTC: Explorer 1 launch on the Jupiter-C rocket

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 8/34 ➔ ESAC – SCIENCE SEMINAR First Measurements

Explorer 3, March 26th, 1958:

• 190 – 2800 km altitude orbit

• Proton belt discovery confirmation

Pioneer 3, December 6th 1958:

• Failed lunar flyby mission: orbit apogee 102’360 km

• Outer electron belt discovery => Van Allen Belts

They could have been called the ”Vernov Belts”

• Sputnik 2, November 3rd, 1957, Laika

• No data… on time!

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 9/34 ➔ ESAC – SCIENCE SEMINAR Apollo Era

• Clear out proton belt with nuclear bomb, Van Allen, 1962

• NASA refused

• Starfish Prime nuclear test, US defence, July 9th 1962

• 400km altitude

• Added more radiation

As seen from Honolulu. Image courtesy of As seen from plane a few minutes after US Govt. Defense Threat Reduction the explosion. Image courtesy of US Govt. Agency Defense Threat Reduction Agency

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 10/34 ➔ ESAC – SCIENCE SEMINAR Apollo Era

NASA decided to proceed

• Avoid the densest radiation regions

• Quick fly through the belts

• Dosimeter carried by each astronaut

• Mission limits: 400 rads (X-rays), 2.5 rads (� particles)

Apollo 7 8 9 10 11 12 13 14 15 16 17 Mission Skin Dose, 0.16 0.16 0.20 0.48 0.18 0.58 0.24 1.14 0.30 0.51 0.55 rads

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 11/34 ➔ ESAC – SCIENCE SEMINAR The South Atlantic Anomaly

• Discovered in 1958

• Inner proton belt

• ~200 km altitude

• Magnetic centre shift

• Spacecraft Single Events Effects (SEE)

• Flashes in astronauts’ eyes

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 12/34 ➔ ESAC – SCIENCE SEMINAR Space Exploration

Sun, Magnetosphere, and Van Allen belts (Space Weather) in-situ studies:

• NASA

• Cluster II, Geotail, MMS, Van Allen probes, CeREs, and 43 other missions

• ESA

• Cluster, Proba 2, Swarm, Solar Orbiter, etc

Help understanding all physical processes taking place in the magnetosphere

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 13/34 ➔ ESAC – SCIENCE SEMINAR Outline

1. Van Allen Belts Through History • Theorisation, discoveries, in-situ research 2. Physics of Trapped Particles • Physical processes, particle motion, loss mechanisms, and dynamics 3. Overview of the Van Allen Belts • What? Why? How? 4. Models • Goals and examples 5. Conclusion

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 14/34 ➔ ESAC – SCIENCE SEMINAR Lorentz Equation

Lorentz Force FL acting on charged particles:

� = �� + �� × � assuming no electric field

⟹ � = �� × �

⟹ � ⊥ �

Magnetic force only change the direction of the velocity vector!

This property can be used to create a ”magnetic trap”.

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 15/34 ➔ ESAC – SCIENCE SEMINAR ”Magnetic Trap”

Simulation from Dr. Michael R. Gallis, Penn State Schuylkill

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 16/34 ➔ ESAC – SCIENCE SEMINAR ”Magnetic Trap”

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 17/34 ➔ ESAC – SCIENCE SEMINAR Triple Motion

• Motions linked to the ”Magnetic trap”

• Gyration ~ 10-5 – 10-3s

• Bounce ~ 10-1 – 1 s

• Motion linked to the magnetic gradient

• Drift ~ 102 – 104 s

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 18/34 ➔ ESAC – SCIENCE SEMINAR Dynamics

Non-disturbed ideal conditions:

• Predictable trajectories

• Stable Van Allen Belts

However, nature never makes it easy!

• Non-adiabatic conditions

Strong dynamics: Injection, Acceleration, Diffusion, and Loss

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 19/34 ➔ ESAC – SCIENCE SEMINAR Dynamics

Strong variability of the Radiation Belts as seen by the NASA Van Allen Probes at the end of 2003.

ESA UNCLASSIFIED - For Official Use © Nasa Lionel Métrailler | 25/07/2019 | Slide 20/34 ➔ ESAC – SCIENCE SEMINAR Injection

Sun is the main supplier of charges particles

• Solar wind

• Magnetic storms

• CMEs, flares

• Magnetic sub-storms

• Reconnections

ESA UNCLASSIFIED - For Official Use © Nasa Lionel Métrailler | 25/07/2019 | Slide 21/34 ➔ ESAC – SCIENCE SEMINAR Transport and Acceleration

• Magnetic gradients

• Triple motion

• Ring currents

• Ultra Low Frequency (ULF) waves

• Magnetospheric resonance

• Very Low Frequency (VLF) waves

• Plasmaspheric resonance

• Human induced radio signals

• ElectroMagnetic Ion Cyclotron (EMIC) Waves

• In the plasmasphere

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 22/34 ➔ ESAC – SCIENCE SEMINAR Particle Loss

Loss of trapped particle • Accelerated and lost in space • Precipitation into the atmosphere

The loss cone Mirror points • high pitch angle - mirror points closer to equator

=> trapped

• low pitch angle - mirror points in atmosphere

=> lost (aurora)

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 23/34 ➔ ESAC – SCIENCE SEMINAR Outline

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 24/34 ➔ ESAC – SCIENCE SEMINAR Earth’s Radiation Belts

• What are they?

• Result of solar wind, solar events, cosmic rays, Earth magnetosphere, and Earth atmosphere complex interactions

• Inner proton belt, ”stable”

• ~10 - 100 MeV

• ~500 - 6,000 km altitude

• Outer electron belt, dynamic

• ~100 keV - 10 MeV

• ~10,000 - 40,000 km altitude

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 25/34 ➔ ESAC – SCIENCE SEMINAR Earth’s Radiation Belts

• Why study them?

• Space Weather

• Understand their dynamics

• Mitigate possible hazards

• Main Risks

• Single Events Effects (SEEs)

• Deep-dielectric charging

• Surface charging

• Radiation dose

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 26/34 ➔ ESAC – SCIENCE SEMINAR Earth’s Radiation Belts

How to study them?

• Laboratory Experiments

• Limited by the setup

• In-Situ

• Limited by the number of satellites and volume to cover

• Theoretically

• Limited by the complexity and the dynamics of the VAB

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 27/34 ➔ ESAC – SCIENCE SEMINAR Outline

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 28/34 ➔ ESAC – SCIENCE SEMINAR Variety of Models

Different approaches - different goals:

• Coverage: local or global for electrons or protons

• Time dependences: static or dynamic, precise and short or rough and long time predictions

• Coordinates: 3D Solar Magnetic, 2D McIlwain’s coordinate systems

• Source: theoretical or data-driven model

• Parameters: use of external space weather parameters or not

• …

A wide variety of models is possible depending on one’s needs!

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 29/34 ➔ ESAC – SCIENCE SEMINAR Some models

British Atlantic Survey – Radiation Belt Model BAS-RBM, 2013 • e-, global, dynamic, theory- & data-driven model, external parameters, McIlwain’s (B, L*) Global Radiation Earth ENvironment model GREEN, 2018, ONERA & CNES • e-, p, global, collection of various existing models, McIlwain’s (B, L*) Electron Slot Region Radiation Environment Model e-SRREM, 2014, Consortium (ESA) * • e-, slot region, data-driven model, McIlwain’s (αeq, L ) AE8 min/max, 1991, AP8 min/max, 1976, USA (NASA) • Most well known, electrons 0.04 – 7 MeV and protons 0.1 – 400 MeV, McIlwain’s (B, L) IRENE-AE9/AP9, 2013, USA (NASA) • Update of the AE8/AP8 models • Electrons 0.04 – 10 MeV and protons 0.1 MeV – 2 GeV, McIlwain’s (B, L*)

We want an easy-to-use model and tailor-made for INTEGRAL and XMM-Newton!

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 30/34 ➔ ESAC – SCIENCE SEMINAR Some models

5D Radiation Belt Model (5DRMB) for trapped electrons

• With/for XMM and INTEGRAL

• Electron 0.7-1.75 MeV

• 3D Solar Magnetic

• Global semi-dynamic data-driven model

• No external parameters needed

• Long-term radiation characterisation

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 31/34 ➔ ESAC – SCIENCE SEMINAR

GPS-2R 12 spacecraft • 20’500 km altitude • 55˚ inclination

Good comparative results

Métrailler, L. et al., 2018, Data-Driven Modelling of the Van Allen Belts: The 5DRBM Model for trapped Electrons, Advances in Space Research, ASR-D-19-00407R1

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Conclusion

Main historical dates: • Earth magnetic field discovery, <1000, compass • Sun – Magnetic Storms – Aurora, Sep 1, 1859, Carrington event • Radiation Belts discovery, 1958, Explorer and Pioneer programs Physics: • Triple motion of charged particles (gyration, bounce, drift) • Non-adiabatic processes (acceleration, diffusion, loss) • Injection of energetic particles (flares, CMEs, reconnections) • Highly dynamic (wave-particle interactions) Models • Large variety of models with different goals • 5DRBM for trapped electrons (INTEGRAL & XMM)

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 33/34 ➔ ESAC – SCIENCE SEMINAR

Thank you for your attention

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 34/34 ➔ ESAC – SCIENCE SEMINAR The South Atlantic Anomaly

Count rate of protons and electrons greater than 0.5 MeV in low Earth orbit measured by the NASA/SAMPEX satellite.

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 35/34 ➔ ESAC – SCIENCE SEMINAR Particle Loss

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 36/34 ➔ ESAC – SCIENCE SEMINAR Coordinate systems McIlwain’s coordinate system * • 2D (B, L) or (αeq, L ) • B is the magnetic intensity along the magnetic field line • L is the equatorial radius of a drift shell • Non trivial transformation to 3D coordinates • Not ideal for asymmetries in the VAB • Not ideal for visualisations • Excellent to increase statistics • Good link with physics

ESA UNCLASSIFIED - For Official Use Lionel Métrailler | 25/07/2019 | Slide 37/34 ➔ ESAC – SCIENCE SEMINAR Coordinate systems

Solar Magnetic coordinate system • 3D (x, y, z) • z axis: Earth magnetic dipole axis • x axis: in the plane containing z and the Earth-Sun line, pointing towards the Sun • y axis: to have an orthogonal system • Not ideal for good statistics, need a lot of data • Not easy to relate to physics => for data- driven models • Good for asymmetries in the VAB • Good for intuitive visualisation • Trivial conversion of coordinates SM à GEI

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